The overall objective of this research program is to develop, validate and utilize (e.g., for treatment research) a system-level model of chronic developmental stuttering. This proposal is the product of a five-year collaboration between the PI and Co-PI that is based on the integration of fluency induction (PI's expertise) with functional (PET) and anatomical (MRI) neuroimaging (Co-PI's expertise) Through this collaboration, stuttering and induced fluency have been studied in a single population (men who stutter and experience fluency during chorus reading), with a single speech task (oral reading) and with a single fluency inducting procedure (chorus reading). From these data, focal physiological abnormalities have been identified (Fox et al., 1996), confirmed to be state rather than trait abnormalities (Ingham et al., 1996), strongly associated with stuttering through performance correlation analysis, and modeled as a system of weighted, regional intercorrelations (see C.3). We now propose to test the generality of these findings by applying this integrative mapping and modeling strategy to additional populations, to an additional speech task, and with an additional fluency inducing procedure. The following hypotheses guide this proposal. Hypothesis One: Stuttered speech is characterized by a consistent pattern of abnormal activations/deactivations of motor/auditory regions. That is, the observations of our previous study (Fox et al. 1996) will generalize across populations and across speech tasks. Hypothesis Two: Stuttered speech is characterized by a stable pattern of interregional instructs that depict the neural system associated with stuttering. That is, the regional intercorrelations mapping a neural system of stuttering that were developed in our prior studies will generalize across populations and across speech tasks. Three experiments are planned to test these hypotheses. Each experiment is supported by preliminary research. The investigators' preliminary research has clearly demonstrated regional abnormal activations in the motor and auditory system during stuttering that are (largely) normalized during fluency induction. Performance correlations analyses (see below) strongly support Hypothesis One. A nascent system model derived from regional intercorrelation matrix analyses offers the basis for Hypothesis Two.